1. Field of the Invention
The present invention relates to data recording and reproducing methods for a write-once read-many type (WORM) recording medium, especially, of a type comprising a recording area including a user data region for storing user data and an index data region for storing index data. The user data includes user data items and the index data comprises index data items.
2. Description of the Related Art
The term "user data" is defined as a type of data relating to the user of the WORM type recording medium, for example, name and age of the user, which may be stored in accordance with the usage of the medium. The term "index data" is defined as a type of data necessary for retrieving a desired user data item such as file name of a user data item, address of the first track on which the user data item is recorded, or the like.
Data recording and reproducing methods of the above-described type is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 61-279957. Now, the methods of the publication will be described with reference to FIG. 1. Since the recording method is similar to the reproduction, only the recording method will be explained for the sake of simplification.
FIG. 1 depicts a rectangular optical card 50 (to be simply called "card" hereinafter), i.e., a write-once read-many type recording medium. On the upper surface of the card 50, a number of tracks 52 arranged in parallel with each other are formed along the longitudinal direction of the card 50. The tracks 52 are located within a data recording area 54.
Data is recorded on each of the tracks 52 in the following manner. A light spot 55 is irradiated on a part of one of the tracks 52 by means of an optical head (not shown) serving as a recording head, and the light spot is moved along the same track 52.
The user data and index data are alternately recorded. More specifically, a user data item is first recorded, and then an index data item corresponding thereto is recorded. After that, another user data item is recorded, and then an index data item corresponding thereto is recorded. The recording performed in the above-described manner will be called hereinafter "alternate recording".
The recording of the user data starts from a track 52a located at the farthest position on the minus (-) side of the recording region 54, whereas the recording of the index data starts from a track 52c located at the farthest position on the plus (+) side of the recording region 54.
As the user data is recorded in the alternate recording proceeds, the recording of the user data is carried out in the following manner. For example, when the recording on the track 52a is completed, the recording moves on to the track 52b adjacent to the track 52a in the plus (+) direction. In the same manner, the recording of the user data proceeds from the track 52a located at the farthest position on the minus (-) side consecutively to tracks located in the plus (+) direction, thus forming a user data region 56 in the recording area 54 from the minus (-) to plus (+) side.
As the alternate recording progresses, the index data is recorded in a similar fashion to the above. For example, when the recording on the track 52c is completed, the recording moves on to the track 52d adjacent to the track 52c in the minus (-) direction. In the same manner, the recording off the index proceeds from the track 52c located at the farthest position on the plus (+) side consecutively to tracks located in the minus (-) direction, thus forming an index data region 58 in the recording area 54 from the plus (+) to minus (-) side.
In the above-described conventional method, the recordings of the user data and the index data start from the tracks 52a and 52c, respectively, each located at one end of the card 50. In general, each user data item and an index data item corresponding thereto are alternately recorded. As a result, when the recording is carried out by the conventional method, the light spot 55 inevitably must travel a large distance in the direction perpendicular to the tracks 52, increasing the time required for recording. The reproduction of data recorded on a medium by the conventional method involves a procedure similar to the aforementioned recording, so it takes much time to reproduce the data.
It is also possible that a given number of user data items are first recorded, and a number of index data items corresponding thereto are then recorded, without conducting the alternate recording of user data and index data. However, this is also the case that the travel distance of the light spot 55 along the direction perpendicular to the tracks 52 is long.